Figure 3b. Noguchi type B adenocarcinoma (localized BAC with foci of alveolar collapse) in a 48-year-old man. (a) Transaxial thin-section (1-mm collimation) CT scan (lung window) obtained at the level of the aortic arch shows a 20-mm nodular area of ground-glass attenuation in the left upper lobe. Note that the lesion has a solid component (arrow). (b) Low-power photomicrograph (original magnification, x12; H-E stain) of a surgical specimen shows thickening of the alveolar walls with tumor cell replacement (lepidic growth). Note the foci of alveolar collapse (arrows). At CT, the foci of lepidic growth appeared as areas of ground-glass attenuation, whereas the foci of alveolar collapse corresponded to the solid component of the lesion. The surgical specimens showed no hilar or mediastinal nodal metastasis, and no recurrence was seen at postoperative follow-up.